/*
 This source file is part of the Swift.org open source project

 Copyright (c) 2021 Apple Inc. and the Swift project authors
 Licensed under Apache License v2.0 with Runtime Library Exception

 See https://swift.org/LICENSE.txt for license information
 See https://swift.org/CONTRIBUTORS.txt for Swift project authors
*/

/// A link to a symbol.
///
/// Symbol links are written the same as inline code spans but with
/// two backticks `\`` instead of one. The contents inside the backticks become
/// the link's destination.
///
/// Symbol links should be typically rendered with "code voice", usually
/// monospace.
public struct SymbolLink: InlineMarkup {
  public var _data: _MarkupData

  init(_ raw: RawMarkup) throws {
    guard case .symbolLink = raw.data else {
      throw RawMarkup.Error.concreteConversionError(from: raw, to: SymbolLink.self)
    }
    let absoluteRaw = AbsoluteRawMarkup(
      markup: raw, metadata: MarkupMetadata(id: .newRoot(), indexInParent: 0))
    self.init(_MarkupData(absoluteRaw))
  }

  init(_ data: _MarkupData) {
    self._data = data
  }
}

// MARK: - Public API

extension SymbolLink {
  /// Create a symbol link with a destination.
  public init(destination: String? = nil) {
    try! self.init(.symbolLink(parsedRange: nil, destination: destination ?? ""))
  }

  /// The link's destination.
  public var destination: String? {
    get {
      guard case let .symbolLink(destination) = _data.raw.markup.data else {
        fatalError("\(self) markup wrapped unexpected \(_data.raw)")
      }
      return destination
    }
    set {
      if let newDestination = newValue, newDestination.isEmpty {
        _data = _data.replacingSelf(.symbolLink(parsedRange: nil, destination: nil))
      } else {
        _data = _data.replacingSelf(.symbolLink(parsedRange: nil, destination: newValue))
      }
    }
  }

  // MARK: Visitation

  public func accept<V: MarkupVisitor>(_ visitor: inout V) -> V.Result {
    return visitor.visitSymbolLink(self)
  }

  // MARK: PlainTextConvertibleMarkup

  public var plainText: String {
    return "``\(destination ?? "")``"
  }
}
